Sediment Bacterial Communities Research Articles

Spatial distribution and assembly processes of bacterial communities in riverine and coastal ecosystems of a rapidly urbanizing megacity in China

Rapid urbanization has precipitated significant anthropogenic pollution (nutrients and pathogens) in urban rivers and their receiving systems, which consequentially disrupted the compositions and assembly of bacterial community within these ecosystems. However, there remains scarce information regarding the composition and assembly of both planktonic and benthic bacterial communities as well as pathogen distribution in such environments. In this study, full-length 16S rRNA gene sequencing was conducted to investigate the bacterial community composition, interactions, and assembly processes as well as the distribution of potential pathogens along a riverine-coastal continuum in Shenzhen megacity, China. The results indicated that both riverine and coastal bacterial communities were predominantly composed of Gammaproteobacteria (24.8 ± 12.6 %), Alphaproteobacteria (16.1 ± 9.8 %), and Bacteroidota (14.3 ± 8.6 %), while sedimentary bacterial communities exhibited significantly higher diversity compared to their planktonic counterparts. Bacterial community patterns exhibited significant divergences across different habitats, and a significant distance-decay relationship of bacterial community similarity was particularly observed within the urban river ecosystem. Moreover, the urban river ecosystem displayed a more complex bacterial co-occurrence network than the coastal ecosystem, and a low ratio of negative:positive cohesion suggested the inherent instability of these networks. Homogeneous selection and dispersal limitation emerged as the predominant influences on planktonic and sedimentary bacterial communities, respectively. Pathogenic genera such as Vibrio, Bacteroides, and Acinetobacter, known for their roles in foodborne diseases or wound infection, were also identified. Collectively, these findings provided critical insights into bacterial community dynamics and their implications for ecosystem management and pathogen risk control in riverine and coastal environments impacted by rapid urbanization.

Bacterial Community Structure of Typical Lake Sediments in Yinchuan City and Its Response to Heavy Metals

Lake wetlands are extremely important and special ecosystems, which are important for regional water resource storage, environmental protection, and biodiversity maintenance. Sediment bacteria are an important component of lake ecosystems and are a major driver of biogeochemical cycling in lakes. In order to investigate the community structure of bacteria in typical lake sediments in Yinchuan City and their influencing factors, three typical lakes in Yinchuan City (Yuehai Lake, Mingcui Lake, and Xiniu Lake) were selected for the study and surface sediments were collected in January, April, July, and October 2021. The composition of the sediment bacterial community was examined using 16S rDNA high-throughput sequencing technology, and the response relationships between them and heavy metals were explored. The results showed that the ecological hazard coefficient for heavy metals in the sediments of three typical lakes in Yinchuan City was far less than 40, and the ecological hazard index was far less than 150, all of which indicated a minor ecological hazard. There were no significant differences in bacterial community diversity among the three lakes, but there were significant variations in diversity among the lakes in different seasons and significant differences in community composition. The dominant phyla (top three in terms of relative abundance) in Yuehai Lake, Mingcui Lake, and Xiniu Lake were Proteobacteria, Bacteroidetes, and Chloroflexi. The dominant lower orders were Gammaproteobacteria, Alphaproteobacteria, and Deltaproteobacteria. The main divergent species that occurred at the phylum level in typical lakes in Yinchuan were Proteobacteria, Bacteroidetes, Euryarchaeota, Firmicutes, Actinobacteria, and Acidobacteria. The sediment bacterial community structure of Yuehai Lake was significantly correlated with Cu, Fe, Mn, Zn, As, and Pb; the sediment bacterial community structure of Lake Mingcui was significantly correlated with Fe, Pb, and Cr; and the sediment bacterial community structure of Xiniu Lake was not significantly correlated with heavy metals. The types and contents of sediment heavy metals had a significant effect on the bacterial community structure of sediments in Yinchuan Yuehai Lake and Mingcui Lake and were important environmental factors that caused changes in the bacterial community structure of lake sediments.

Exploring di (2-ethylhexyl) phthalate degradation by a synthetic marine bacterial consortium: Genomic insights, pathway and interaction prediction, and application in sediment microcosms

Di (2-ethylhexyl) phthalate (DEHP), a toxic phthalate ester (PAE) plasticizer, is often detected in marine sediment and biota. Our understanding of DEHP-degrading marine bacteria and the associated genetic mechanisms is limited. This study established a synthetic bacterial consortium (A02) consisting of three marine bacteria (OR05, OR16, and OR21). Consortium A02 outperformed the individual strains in DEHP degradation. Investigations into the degradation of DEHP intermediates revealed that OR05 and OR16 likely contributed to enhanced DEHP degradation by Consortium A02 via the utilization of DEHP intermediates, such as protocatechuic acid and mono (ethylhexyl) phthalate, with OR21 as the key DEHP degrader. A pathway of DEHP degradation by Consortium A02 was predicted based on genome analysis and experimental degradation. Bioaugmentation with Consortium A02 led to 80% DEHP degradation in 26 days in saline sediment (100 mg/kg), surpassing the 53% degradation by indigenous microbes, indicating the potential of A02 for treating DEHP-contaminated sediments. Meanwhile, bioaugmentation notably changed the bacterial community, with the exclusive presence of certain bacterial genera in the A02 bioaugmented microcosms, and was predicted to result in a more dynamic and active sediment bacterial community. This study contributes to the limited literature on DEHP degradation by marine bacteria and their associated genes.

Cyanobacterial bloom affects structural and functional succession of microbial communities in urban wetland sediments in the Qinghai Plateau

Abstract Algal blooms significantly affect microbial communities in wetland ecosystems. However, little is known about the succession of sediment microbial communities during algal blooms. This study aimed to investigate the temporal patterns of sediment bacterial community structure and function succession during algal blooms (March to May 2022) with high-throughput sequencing technology. To this end, algal blooms were divided into the bloom stage (BS), decomposition stage (DS) and end stage (ES). The results showed that: (i) The algal blooms were dominated by Microcystis species within Cyanobacteria. Both phytoplankton abundance and biomass reached the peak in the BS, with 45.78 × 105 cells/L and 5.97 mg/L, respectively. (ii) The alpha diversity indices of the sediment bacterial community showed a monotonically increasing trend, with the lowest value in the BS. Cyanobacterial blooms reduced the relative abundance of Actinobacteria and Chloroflexi, and raised that of Firmicutes, Proteobacteria and Bacteroidetes. (iii) Cyanobacterial blooms remarkably decreased the complexity of the co-occurrence network of the sediment bacterial community, which resisted extreme environmental conditions in the BS and DS by increasing positive relationships. (iv) Mantel test showed that phytoplankton biomass, T, dissolved oxygen and organic carbon had significant effects on the sediment bacterial community. The results of this study are important for the ecological management of algal blooms through microorganisms.

Quantitative effects of anthropogenic and natural factors on the spatial distribution of heavy metals and bacterial communities in sediments of the Pearl River Delta

Heavy metal (HM) contamination of aquatic ecosystems has increasingly posed threats to ecological balance and health. Analysis of sediments to determine water pollution sources is widely reported, while quantitative research about the effects of environmental factors on the distribution of HMs and relevant microbial communities is limited. Here, we investigated 6 kinds of HM pollution characteristics (As, Cd, Cr, Cu, Pb, and Zn) of the Pearl River Delta (PRD) by collecting surface sediment samples around the main stream and estuary and explored the influencing factors with a geographical detector method (GDM). The shifts in the corresponding microbial community was further analyzed, and the influence mechanism was clearly elucidated using partial least squares path modeling (PLS-PM). Results showed that (i) most HM contents of the sediments greatly exceeded the local background values, wherein, Cd had the highest pollution level; (ii) temperature was considered the dominant natural factor of HM distribution, except for Pb, with an influence degree of 0.68–0.97; (iii) industrial activity is an significant anthropogenic factor for HM distribution, and the electroplating industry was the main source for Cr, Cu and Zn; (iv) the network analysis revealed that As, Cu and Cr were enriched in some HM-tolerant bacteria (mainly Chloroflexi, Acidobacteriota and Proteobacteria), while heavy Cd pollution induced a reduction in sensitive bacterial taxa; (v) PLS-PM demonstrated that human activities largely affect bacterial communities by causing HM pollution. This study could provide guidance for better management of HM pollution control practices, such as specific industrial governance and layout optimization.

Response of the microbial community structure to the environmental factors during the extreme flood season in Poyang Lake, the largest freshwater lake in China.

Poyang Lake is the largest freshwater lake in China, and there are several studies on the composition and diversity of bacteria in Poyang Lake, while few quantitative studies were carried out on the response of the bacterial community to environmental factors during the extreme flood season in Poyang Lake. The connected-lake heterogeneity of bacterial community composition (BCC) was investigated in Poyang Lake during the flood season in 2020. Illumina high-throughput sequencing technology was used in this study. The bacterial community structure in the water was different from that in the sediment of Poyang Lake during extreme flood seasons. The bacterial diversity in water was much lower than that in sediment. In the water column, the dominant phyla were Actinobacteriota, while the composition of bacteria in sediment was more complex than that in water, and the dominant phyla in sediment were Proteobacteria, Chloroflexi, Acidobacteriota, and Actinobacteriota. The bacterial diversity in the water of Poyang Lake showed seasonal dynamics, while no seasonal variation of bacterial communities in sediment was observed. The bacterial community structure in the sediment from the two bays and channel areas of Poyang Lake can be distinguished from each other. The microbial diversity in sediment gradually increased from the Sancha Bay to the Zhouxi Bay and then to the channel, but the total nitrogen (TN) concentration in sediment (STN) and the total phosphorus (TP) concentration in sediment (STP) showed opposite trends. This might be due to the anthropogenic disturbances from the extreme flood. The bacterial community structure in, water column was significantly correlated with WT, NH4-N, STP, SOM, Chl a, DO, TP, and Eh, while the bacterial community structure in sediment was significantly correlated with SOM and STP. The bacterial community structure in water was greatly different from that in sediment in Poyang Lake during extreme flood seasons. The bacterial community structure in the water column was not only sensitive to the geochemical characteristics of the water but also affected by some nutrient concentrations in the sediment. During the wet seasons, bacterial diversity was only affected by SOM and STP.

Effects of microplastics on the structure and function of bacterial communities in sediments of a freshwater lake

As an emerging pollutant, microplastics (MPs) cause widespread concern around the world owing to the serious threat they pose to ecosystems. In particular, sediments are thought to be the long-term sink for the continual accumulation of MPs in freshwater ecosystems. Polyethylene (PE) and polyethylene terephthalate (PET) have been frequently detected with large concentration variations in freshwater sediments from the lower reaches of the Yangtze River, one of the most economically developed regions in China, characterized by accelerated urbanization and industrialization, high population density and high plastics consumption. However, the impact of PE and PET on the sedimental bacterial community composition and its function has not been well reported for this specific region. Herein, PE and PET particles were added to freshwater sediments to assess the effects of different MP types on the bacterial community and its function, using three concentrations (500, 1500 and 2500 items/kg) per MP and incubations of 35, 105 and 175 days, respectively. This study identified a total of 68 phyla, 211 classes, 518 orders, 853 families and 1745 genera. Specifically, Proteobacteria, Chloroflexi, Acidobacteriota, Actinobacteriota and Firmicutes were the top five phyla. A higher bacterial diversity was obtained in control sediments than in the MP-treated sediments. The presence of MPs, whether PET or PE, had significant impact on the bacterial diversity, community structure and community composition. PICRUSt2 and FAPOTAX predictions demonstrated that MPs could potentially affect the metabolic pathways and ecologically functional groups of bacteria in the sediment. Besides the MP-related factors, such as the type, concentration and incubation time, the physicochemical parameters had an effect on the structure and function of the bacterial community in the freshwater sediment. Taken together, this study provides useful information for further understanding how MPs affect bacterial communities in the freshwater sediment of the lower reaches of the Yangtze River, China.

Response of bacterial and micro-eukaryotic communities to spatio-temporal fluctuations of wastewater in full scale constructed wetlands

How microbial communities respond to wastewater fluctuations is poorly understood. Full-scale surface flow constructed wetlands (SFCWs) were constructed for investigating microbial communities. Results showed that influent wastewater changed sediment bacterial community composition seasonally, indicating that a single bacterial taxonomic group had low resistance (especially, Actinobacteriota and Gammaproteobacteria). However, copy numbers of 16S rRNA, ammonia oxidizing archaea, ammonia oxidizing bacteria, nirS and nirK in the first stage SFCWs were 2.49 × 1010, 3.48 × 109, 5.76 × 106, 8.77 × 108 and 9.06 × 108 g−1 dry sediment, respectively, which remained stable between seasons. Moreover, decreases in the nitrogen concentration in wastewater, changed microbial system state from heterotrophic to autotrophic. Micro-eukaryotic communities were more sensitive to wastewater fluctuations than bacterial communities. Overall, results revealed that microbial communities responded to spatio-temporal fluctuations in wastewater through state changes and species asynchrony. This highlighted complex processes of wastewater treatment by microbial components in SFCWs.

Characteristics of bacterial community structure in the sediment of Chishui River (China) and the response to environmental factors

Sediment microorganisms performed an essential function in the biogeochemical cycle of aquatic ecosystems, and their structural composition was closely related to environmental carrying capacity and water quality. In this study, the Chishui River (Renhuai section) was selected as the research area, and the concentrations of environmental factors in the water and sediment were detected. High⁃throughput sequencing was adopted to reveal the characteristics of bacterial community structures in the sediment. In addition, the response of bacteria to environmental factors was explored statistically. Meanwhile, the functional characteristics of bacterial were also analyzed based on the KEGG database. The results showed that the concentration of environmental factors in the water and sediment displayed spatial differences, with the overall trend of midstream > downstream > upstream, which was related to the wastewater discharge from the Moutai town in the midstream directly. Proteobacteria was the most dominant phylum in the sediment, with the relative abundance ranged from 52.06% to 70.53%. The distribution of genus-level bacteria with different metabolic activities varied in the sediment. Upstream was dominated by Massilia, Acinetobacter, and Thermomonas. In the midstream, Acinetobacter, Cloacibacterium and Comamonas were the main genus. Nevertheless, the abundance of Lysobacter, Arenimonas and Thermomonas was higher in the downstream. Redundancy analysis (RDA) showed that total nitrogen (TN) and total phosphorus (TP) were the main environmental factors which affected the structure of bacterial communities in sediment, while total organic carbon (TOC) was the secondary. The bacterial community was primarily associated with six biological pathway categories such as metabolism. Carbohydrate metabolism and amino acid metabolism were the most active functions in the 31 subfunctions. This study could contribute to the understanding of the structural composition and driving forces of bacteria in the sediment, which might benefit for the ecological protection of Chishui River.

Microplastics enhance the invasion of exotic submerged macrophytes by mediating plant functional traits, sediment properties, and microbial communities

Plant invasions and microplastics (MPs) have significantly altered the structure and function of aquatic habitats worldwide, resulting in severe damage to aquatic ecosystem health. However, the effects of MPs on plant invasion and the underlying mechanisms remain largely unknown. In this study, we conducted mesocosm experiments over a 90-day period to assess the effects of polystyrene microplastics on the invasion of exotic submerged macrophytes, sediment physicochemical properties, and sediment bacterial communities. Our results showed that PS-MPs significantly promoted the performance of functional traits and the invasive ability of exotic submerged macrophytes, while native plants remained unaffected. Moreover, PS-MPs addition significantly decreased sediment pH while increasing sediment carbon and nitrogen content. Additionally, MPs increased the diversity of sediment bacterial community but inhibited its structural stability, thereby impacting sediment bacterial multifunctionality to varying degrees. Importantly, we identified sediment properties, bacterial composition, and bacterial multifunctionality as key mediators that greatly enhance the invasion of exotic submerged macrophytes. These findings provide compelling evidence that the increase in MPs may exacerbate the invasion risk of exotic submerged macrophytes through multiple pathways. Overall, this study enhances our understanding of the ecological impacts of MPs on aquatic plant invasion and the health of aquatic ecosystems.

Bacterial diversity and functional characteristics of natural rainwater lakes in Saihanba artificial forest farm as revealed by 16S rRNA sequencing

The Saihanba Mechanical Forest is an artificial national forest park with a forest-steppe landscape. The flora and fauna have been extensively studied, but a comprehensive understanding of the bacterial community composition and structure of the natural rainwater lakes present in the area has rarely been reported. In this study, the structure and functional characteristics of bacterial communities in lake sediments and water samples in the Saihanba artificial forest were investigated using 16s rRNA high-throughput sequencing. Microbial diversity analyses revealed that Proteobacteria, Acidobacteria, Bacteroidota and Verrucomicrobiota microbiota dominated. The abundance of Proteobacteria and Actinobacteriota was significantly higher (p < .05) in water samples compared to sediment samples. PICRUSt2 functional analysis predicted genes associated with the degradation of xenobiotics and the execution of essential metabolic processes. Here, we report differences in the composition of native bacterial communities in sediments and water under the Saihanba artificial forest and make functional gene predictions. This study provides a reference for further exploring the structure and functional characteristics of microbial communities in water samples and sediment environments of lakes under planted forests.

New insights into bioaugmented removal of sulfamethoxazole in sediment microcosms: degradation efficiency, ecological risk and microbial mechanisms

BackgroundBioaugmentation has the potential to enhance the ability of ecological technology to treat sulfonamide-containing wastewater, but the low viability of the exogenous degraders limits their practical application. Understanding the mechanism is important to enhance and optimize performance of the bioaugmentation, which requires a multifaceted analysis of the microbial communities. Here, DNA-stable isotope probing (DNA-SIP) and metagenomic analysis were conducted to decipher the bioaugmentation mechanisms in stabilization pond sediment microcosms inoculated with sulfamethoxazole (SMX)-degrading bacteria (Pseudomonas sp. M2 or Paenarthrobacter sp. R1).ResultsThe bioaugmentation with both strains M2 and R1, especially strain R1, significantly improved the biodegradation rate of SMX, and its biodegradation capacity was sustainable within a certain cycle (subjected to three repeated SMX additions). The removal strategy using exogenous degrading bacteria also significantly abated the accumulation and transmission risk of antibiotic resistance genes (ARGs). Strain M2 inoculation significantly lowered bacterial diversity and altered the sediment bacterial community, while strain R1 inoculation had a slight effect on the bacterial community and was closely associated with indigenous microorganisms. Paenarthrobacter was identified as the primary SMX-assimilating bacteria in both bioaugmentation systems based on DNA-SIP analysis. Combining genomic information with pure culture evidence, strain R1 enhanced SMX removal by directly participating in SMX degradation, while strain M2 did it by both participating in SMX degradation and stimulating SMX-degrading activity of indigenous microorganisms (Paenarthrobacter) in the community.ConclusionsOur findings demonstrate that bioaugmentation using SMX-degrading bacteria was a feasible strategy for SMX clean-up in terms of the degradation efficiency of SMX, the risk of ARG transmission, as well as the impact on the bacterial community, and the advantage of bioaugmentation with Paenarthrobacter sp. R1 was also highlighted.8sNhd6qoUNMdHWMUGzd-tFVideo

Exploring the depths: Metagenomic profiling of cold seep bacterial communities and isolation of hydrocarbon-degrading microbes from the Cauvery-Mannar basin

Cold seeps are unique ecosystems characterized by the presence of endemic communities reliant on microorganisms that survive through chemosynthesis, utilizing sulfide, methane, hydrocarbons, and other reduced compounds. Recently, a cold seep was discovered in the Cauvery-Mannar basin during an expedition aboard the research vessel ORV Sindhu Sadhana which led to the investigation into the distribution and isolation of microorganisms within the sediment layers (0–6 cm). Metagenomic analysis based on V3-V4 region of the sediment's bacterial community revealed a prevalence of bacteria associated with methane and hydrocarbons. Dominant phyla included Campilobacterota (20–25%), Proteobacteria (15–25%), Firmicutes (15-20%), Desulfobacterota (10–18%), Chloroflexi (5–10%), and Actinobacterota (5–7%). In-vitro isolation of hydrocarbon-degrading bacteria using minimal media supplemented with 1% crude oil gave rise to 15 bacterial strains. Molecular identification of six isolates (chosen based on the dense growth obtained in agar plates) revealed their affiliation with the genera Acinetobacter, Rhodococcus, Acinetobacter, and Bacillus. This comprehensive study constitutes the first report on the bacterial community structure found in sediments from a cold seep of Cauvery-Mannar basin, along with the successful isolation and identification of hydrocarbon-degrading bacteria.

Unraveling the role of bacterial communities in mangrove habitats under the urban influence, using a next-generation sequencing approach

Mangrove ecosystems are vital coastal habitats with rich biodiversity and play a significant role in carbon sequestration, these habitats are facing mounting threats from rapid urbanization. This study delves into assessing the sediment bacterial communities from the urban mangrove habitats of Campal and Panaji, within the Mandovi estuarine environment of Goa, to understand the intricate interplay between urbanization and bacterial dynamics in the mangrove habitats. We used a combined approach of 16S amplicon and shotgun sequencing methodologies to understand the bacterial taxonomic composition and functional profiles. The community structure revealed the dominance of bacterial groups from phylum Proteobacteria, Chloroflexi and Actinobacteria at both locations. The impact of urbanization was evident from the increased abundance of pathogenic groups at class and genus levels in this region. The core microbiome analysis showed the presence of Shewanella, Pseudomonas and Clostridium which are mostly pathogenic, anaerobic taxa Woeseia, Rheinheimera, like genera that are involved in the organic matter cycling and unclassified bacteria. Though increased pathogenic forms are reported, it is evident that the dominant taxa also included groups that contributed to the biogeochemical cycling of organic matter in sediment from these locations. Functional diversity elucidated through shotgun metagenomics analysis showcased the predominance of carbohydrate metabolism and the presence of glycoside hydrolases degrading plant-based starch, pectin and cellulosic organic matter. The occurrence of xenobiotic biodegradation pathways is an indication of the presence of xenobiotic degrading microbes as a natural means of degrading high amounts of pollutants at this location. Comparative analysis of the metagenomes from this study with similar earlier studies at Ribandar, Mandovi and Cortalim, Zuari mangrove habitats of Goa with varying pollution levels also reiterates the terrestrial influence on the microbial community in these habitats. It showed that Panaji and Campal locations had the presence of dominant pathogenic forms which was absent in the other two locations. The Ribandar and Coratlim location which is reported to have a comparatively lesser impact due to anthropogenic activity had an increased abundance of distinct genera which are predominant heterotrophic forms involved in remineralization and reduced levels of pathogens. Our findings highlight the profound influence of urbanization on the sediment mangrove bacterial communities and spotlight the resilience and adaptability of these microorganisms. This calls for immediate action and preventive measures to restore their functional potential in maintaining the health of these ecosystems amidst expanding urban landscapes.

Probing the microbiome in stormwater pipeline sediments: Co-occurrence patterns and novel functionalities

Stormwater pipeline is an essential pathway to transfer stormwater runoff into nearby receiving water bodies. Understanding the composition, co-occurrence patterns, and function of the microbial communities in stormwater pipeline sediments can help to provide management and control strategies for stormwater runoff pollution to safeguard water safety and ecological health of the urban water environment. This study employs 16S rRNA gene amplicon sequencing to probe the microbial communities in stormwater pipeline sediments of a highly urbanized area in Guangzhou, China. Results show that the sediment bacterial community is rich in Listeria, Prevotella, Stenotrophomonas, and Pseudomonas, which all pertain to pathogens. Methanogens (Methanobacterium, Methanosaeta, Methanosarcina, and Methanobrevibacter) and ammonia-oxidizing archaea (Ca. Nitrosopelagicus, Ca. Nitrososphaera, and Ca. Nitrosotenuis) dominated the archaeal community in stormwater pipeline sediments. These microbial functions are further validated by the function prediction of the overall microbial community. The co-occurrence network and microbe-environment correlation analyses suggest that particulate C-N-P components play a more crucial role, in comparison to dissolved ones in regulating the sediment microbiome, although not all samples follow this mechanism. These findings are expected to contribute to the pollution control of stormwater runoff in stormwater pipeline systems and provide valuable guidance for improving the environmental well-being of urban water ecosystems.

Effects of Cascade Reservoirs on Spatiotemporal Dynamics of the Sedimentary Bacterial Community: Co-occurrence Patterns, Assembly Mechanisms, and Potential Functions.

Dam construction as an important anthropogenic activity significantly influences ecological processes in altered freshwater bodies. However, the effects of multiple cascade dams on microbial communities have been largely overlooked. In this study, the spatiotemporal distribution, co-occurrence relationships, assembly mechanisms, and functional profiles of sedimentary bacterial communities were systematically investigated in 12 cascade reservoirs across two typical karst basins in southwest China over four seasons. A significant spatiotemporal heterogeneity was observed in bacterial abundance and diversity. Co-occurrence patterns in the Wujiang Basin exhibited greater edge counts, graph density, average degree, robustness, and reduced modularity, suggesting more intimate and stronger ecological interactions among species than in the Pearl River Basin. Furthermore, Armatimonadota and Desulfobacterota, identified as keystone species, occupied a more prominent niche than the dominant species. A notable distance-decay relationship between geographical distance and community dissimilarities was identified in the Pearl River Basin. Importantly, in the Wujiang Basin, water temperature emerged as the primary seasonal variable steering the deterministic process of bacterial communities, whereas 58.5% of the explained community variance in the neutral community model (NCM) indicated that stochastic processes governed community assembly in the Pearl River Basin. Additionally, principal component analysis (PCA) revealed more pronounced seasonal dynamics in nitrogen functional compositions than spatial variation in the Wujiang Basin. Redundancy analysis (RDA) results indicated that in the Wujiang Basin, environmental factors and in Pearl River Basin, geographical distance, reservoir age, and hydraulic retention time (HRT), respectively, influenced the abundance of nitrogen-related genes. Notably, these findings offer novel insights: building multiple cascade reservoirs could lead to a cascading decrease in biodiversity and resilience in the river-reservoir ecosystem.

Seasonality in land-ocean connectivity and local processes control sediment bacterial community structure and function in a High Arctic tidal flat.

Climate change is altering patterns of precipitation, cryosphere thaw, and land-ocean influxes, affecting understudied Arctic estuarine tidal flats. These transitional zones between terrestrial and marine systems are hotspots for biogeochemical cycling, often driven by microbial processes. We investigated surface sediment bacterial community composition and function from May to September along a river-intertidal-subtidal-fjord gradient. We paired metabarcoding of in situ communities with in vitro carbon-source utilization assays. Bacterial communities differed in space and time, alongside varying environmental conditions driven by local seasonal processes and riverine inputs, with salinity emerging as the dominant structuring factor. Terrestrial and riverine taxa were found throughout the system, likely transported with runoff. In vitro assays revealed sediment bacteria utilized a broader range of organic matter substrates when incubated in fresh and brackish water compared to marine water. These results highlight the importance of salinity for ecosystem processes in these dynamic tidal flats, with the highest potential for utilization of terrestrially derived organic matter likely limited to tidal flat areas (and times) where sediments are permeated by freshwater. Our results demonstrate that intertidal flats must be included in future studies on impacts of increased riverine discharge and transport of terrestrial organic matter on coastal carbon cycling in a warming Arctic.

Dynamics of the sedimentary bacterial communities in a plain river network: similar coalescence patterns with bacterioplankton communities driven by distinct assembly processes.

Microorganisms play important roles in driving the biogeochemical cycles within river ecosystems. It has been suggested that hydrologic conditions could influence microbial communities in rivers, but their specific effects on the behaviours of microbial coalescence have not been thoroughly investigated. In this study, the dynamics of sedimentary bacterial communities within a plain river network were analyzed by amplicon sequencing followed by several ecological models to uncover the underlying assembly processes. Additionally, a comparative analysis between bacterioplankton communities and sedimentary bacterial communities was performed to unveil their coalescence patterns. The results suggested that similar coalescence patterns between sedimentary bacterial and bacterioplankton communities were driven by distinct assembly processes under dynamic hydrological conditions. These findings enhanced our understanding of microbial diversity features within river ecosystems.

Resistance of freshwater sediment bacterial communities to salinity disturbance and the implication for industrial salt discharge and climate change-based salinization

The impact of salinization on freshwater ecosystems became apparent during the 2022 ecological disaster in the Oder River, located in Poland and Germany, which was caused by salt discharge from mining activities. How bacterial communities respond to salinization caused by industrial salt discharge, or climate change-driven events, depends on the sensitivity of these complex bacterial communities. To investigate the sensitivity of bacterial communities to pulse salinization, we performed an experiment in the salinity range from 0.2 to 6.0. In addition, we sampled similar salinities in the littoral zone of the Baltic Sea where the bacterial communities are permanently exposed to the aforementioned salinities. To simulate a major disturbance, we included an ampicillin/streptomycin treatment in the experiment. Although the addition of antibiotics and increase in salinity had a significant impact on the water bacterial richness and community composition, only antibiotics affected the sediment bacterial community in the experiment. In contrast, sediment bacterial communities from the Baltic Sea littoral zone clustered according to salinity. Hence, sediment bacterial communities are more resistant to pulse changes in salinity than water bacteria but are able to adapt to a permanent change without loss in species richness. Our results indicate that moderate pulse salinization events such as industrial salt discharge or heavy storms will cause changes in the water bacterial communities with unknown consequences for ecosystem functioning. Sediment bacterial communities, however, will probably be unaffected in their ecosystem functions depending on the disturbance strength. Long-term disturbances, such as sea level rise or constant salt discharge, will cause permanent changes in the sediment bacterial community composition.

Characteristics of Bacterial Community Structure in the Sediment of Rural Black and Odorous Water Bodies

Sediment microorganisms are the main drivers of the material circulation and organic matter degradation processes in rural black and odorous water bodies(RBOWB), and the community structure of sediment microorganisms follows the changes in the external environment. Here, the pollutant indicators, including nitrogen, phosphorus, and heavy metals in the overlying water and sediment of 29 RBOWB in Dongming County of Heze City were measured, respectively. Combined with Illumina sequencing results, the composition and diversity characteristics of sediment bacterial communities in RBOWB and their correlation with environmental factors were further analyzed. The experimental results showed a wide distribution of pollutants in both of the overlying water and sediment in the RBOWB of this region. Compared with agricultural non-point source pollution, the concentrations of nitrogen and phosphorus pollutants in the overlying water with domestic sewage as the main source of pollution were 3.1 and 1.5 times higher than those of agricultural non-point source pollution, respectively. In addition, the contents of heavy metals in the sediments of RBOWB were generally lower than the soil element background value in Heze City. The dominant bacteria phyla in the sediments of the RBOWB were Proteobacteria, Actinobacteria, Chloroflexi, Firmicutes, and Acidobacteria, and the total abundance of these five dominant phyla accounted for 70.3%-83.6% of all sequences. The dominant classes were γ-Proteobacteria, α-Proteobacteria, Anaerolineae, and Actinobacteria. The dominant genera were Thiobacillus and Pseudarthrobacter. Moreover, Spearman correlation analysis showed that the environmental factors of DO, COD, TN, TP, and organic matter exerted significant effects(P<0.05) on sediment bacterial genera in RBOWB, and sediment bacterial community richness was significantly influenced by TN(P<0.05). The above results provided the microbiological knowledge for treating RBOWB.